The mechanism of producing metallic titanium by electrochemically reducing rutile (TiO2) at high temperatures was studied. First, the oxygen was successfully electroremoved from TiO2 at temperatures 1700, 1750, and 1800°C in molten CaF2 under a stable electrolytic potential of 2.5？V. Second, the electrodeoxidization process was studied with cyclic voltammetry (CV) tests at 1750°C. It was found that the electrochemical reduction for preparing metallic Ti from TiO2 at the high temperatures can be divided into several steps. In other words, the oxygen in TiO2 was electro-removed as a step-by-step pathway (TiO2→Ti4O7→Ti3O5/Ti2O3→TiO→Ti) at different electrolytic potentials. It unraveled the mechanism of electrochemical reduction of TiO2 at the high temperatures, which is helpful for monitoring the reduction procedure. 1. Introduction Titanium and its alloys play an essential role in industry because of their excellent properties of high ratio of strength/weight, fine plasticity, and superior corrosion-resistance [1]. Although Ti has an attractive future in industry, it cannot be widely used due to the high cost and complex production procedure. Until now, the mainly used commercial procedure for Ti production is Kroll process [2], but the Kroll process needs large energy and long time. In the recent decade, FFC Cambridge process was proposed and considered to be an effective alternative method of direct electrochemical reduction of rutile (TiO2) to Ti [3, 4]. In this process, the cathode of TiO2 pellets was immersed into molten CaCl2 and reduced to Ti electrochemically at 900°C under the electrolytic potentials of 2.8–3.2？V. The electrolytic reactions given by this process can be summarized as the following equations: This process has two main advances compared with the traditional Kroll method: first, FFC process is a one-plot technique, thereby less time and less energy are spent; second, it can be applied to produce other metals or alloys by this electrochemical reduction method. For example, until now, many metals and alloys, such as, Cr, Si, Nb, Ni, Zr and Ni-Mn-Ga, Ti-W, and Nb-Si, were produced from their oxides by the electrochemical reduction method [5–14]. However, the most critical challenge to sabotage broad industrial applications of FFC process is low current efficiency and slow reaction rate. For example, the current efficiency was between 30% and 50% in most cases; in only a few experiments it can reach 80% [15]. Moreover, only the TiO2 contacted with the wrapped electrode wires could be completely deoxidized to metallic Ti after
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